Ensuring sufficient enzyme stability during storage represents a problem in the formulation of liquid enzymatic systems such as liquid enzymatic detergents, particularly those containing a detergent builder The problem has received considerable attention in the prior art. One approach has been incorporation of various chemicals as enzyme stabilizers.
Another approach has been to coat or encapsulate the enzyme with a suitable coating agent and disperse the coated enzyme in the liquid detergent.
Thus, the method described in EP-A-0238216 entails dispersing enzymes as particles in liquid detergent which has a structure which prevents sedimentation of the particles, after coating the particles with a hydrophobic, water-insoluble substance such as a silicone which isolates the particles from the aggressive medium. U.S. Pat. No. 4,090,973 describes encapsulating the enzyme in a water-soluble, solid surface active agent, such as polyvinyl alcohol or polyethylene glycol before addition to the liquid detergent. JP-A 63-105,098 describes coating of enzymes with polyvinyl alcohol to form microcapsules and dispersing the capsules uniformly in a liquid detergent to improve storage stability.
The methods according to said publications involve physically surrounding a particle or droplet containing the enzyme with a barrier which isolates the enzyme more or less effectively from the detergent medium. To ensure effective coating or encapsulation of the enzyme with a protective material, a relatively high amount of the latter is required.
One method, described in EP-A 0,238,216, is to protect the enzyme by dispersing it in a hydrophobic liquid which is insoluble in the detergent, such as silicone oil, and dispersing the liquid in the detergent. Another proposed method is to encapsulate the enzyme in non-ionic surfactant (U.S. Pat. No. 4,090,973) or polyvinyl alcohol (GB 1,204,123, JP-A 63-105,098, FR 2,132,216) by physically coating solid particles of enzyme with the encapsulant. JP-A 61-254,244 describes dispersing an enzyme in an aqueous polymer solution, dispersing the latter in a hydrocarbon and precipitating the polymer to form the micro capsules